There is an additional cut in the receiver for the safety sear on select fire receivers. Semi auto receivers normally don't have this cut. Select fire ejector blocks and bolt carriers are allowed. Without the receiver cut, the safety sear won't fit the receiver, even with the military ejector block. The Century castings may be reject castings and this may explain the warped one. Also every one I've seen has the front magazine catch too low in the receiver.

Hey sprat I have been heads-down with real work and haven't done anything else to the blank other than true up the sides. At the rate I'm going this will be a winter project or perhaps next year. So I'm not close to needing the dies but I'll have to ping you when I make more progress

Hey sprat I have been heads-down with real work and haven't done anything else to the blank other than true up the sides. At the rate I'm going this will be a winter project or perhaps next year. So I'm not close to needing the dies but I'll have to ping you when I make more progress

not a problem, I am stalled myself with work and little time to build right now, I am trying to finish what I start. I have a sig P-228 I build that just does not want to work the way I want. I have built 6 so far but this one is driving me crazy, I have done 3 alum frame and 3 steel frame. worst yet its got a mix of aftermarket and factory sig parts, all my builds are with factory sig parts

for you new guys you can't buy 80% sig frames anymore

on another note I just saw a build concept of using a demilled SKS receiver stub and barrel and mounting on a extra FAL lower using AK mags over on weapons guild